1. Field of the Invention
The present invention relates to an ozonizer in which an alternating high voltage is applied to a discharge gap between a high voltage electrode and a low voltage electrode to generate ozone gas.
2. Description of the Related Art
FIG. 25 is a cross sectional drawing of a conventional laminated ozonizer described in, for example, Japanese Patent Publication No. 3113885.
This conventional rectangular parallelopiped ozonizer comprises a base 1, discharge cells 2 laminated in a plurality of layers on the base 1, blocks 3 sandwiching low voltage electrodes 4 of the discharge cells 2 laminated at both sides of the base 1 and a number of fastening bolts 5 passing through the low voltage electrodes 4 and blocks 3, tip portions thereof screwing to integrate the base 1, the discharge cells 2 and the blocks 3.
The discharge cell 2 comprises a high voltage electrode 8, a dielectric 7 contacting both surfaces of the high voltage electrode and a low voltage electrode 4 facing the dielectric 7 via the discharge gap 6. The dielectric 7 is made of glass. The high voltage electrode 8 is made of a conductive sheet such as a stainless steel plate and the like and is connected to a feed terminal (not shown).
A number of spacers 9 are disposed in the discharge gap 6 at a predetermined interval. These spacers 9 comprise rigid bodies and, in FIG. 25, extend in a direction orthogonal to the page. A diameter dimension of the spacers 9 is smaller than a discharge gap length which is inevitably determined by fastening the ozonizer with the fastening bolts 5, and the spacers 9 “float” inside the discharge gap 6.
Moreover, in a case where the spacers in the discharge gap are elastic bodies, a diameter of the spacers is bigger than the discharge gap and the spacers are compressed a little.
The discharge gaps 6 are communicated with an ozone gas outlet portion 10 passing through respective end portions of the blocks 3, low voltage electrodes 4 and base 1 in a laminating direction of the discharge cells 2. A coolant passage 11 is formed in each low voltage electrode 4. An end portion of each coolant passage 11 is connected to a coolant outlet portion 12 passing through the blocks 3, low voltage electrodes 4 and base 1. The coolant outlet portion 12 is formed at a near side in the width direction of the ozonizer (the direction orthogonal to the surface of the page). Also, a coolant inlet portion connected to the coolant passages 11 (not shown) is formed at a far side in the width direction of the ozonizer.
Next, operation will be explained.
When an alternating high voltage is applied between the low voltage electrode 4 and the high voltage electrode 8, a dielectric barrier discharge is generated in the discharge gap 6 via the dielectric 7. Oxygen gas is introduced to the discharge gaps 6 from oxygen gas inlet portions (not shown) formed at both the near side and far side of the page so as to collide at a central portion and is dissociated to single oxygen atoms by this discharge, and, at roughly the same time, a collision is induced between these oxygen atoms and other oxygen molecules and a three body collision is induced between these oxygen atoms, other oxygen molecules and a wall and the like and ozone gas is generated. By continuously supplying oxygen gas to the discharge gaps 6, the ozone gas generated by the discharge may be continuously derived as ozone gas from the ozone gas outlet 10.
An ozone generating efficiency derived from this discharge is normally, at most, 20%. That is to say, 80% of the discharge power heats the electrodes and is lost. Also, the generating efficiency of the ozone gas is dependent on the temperature of the electrode 4, 8 (strictly speaking, the temperature of the oxygen gas and the ozone gas in the discharge gap), and the lower the temperature of the electrode the higher the generating efficiency. Hence, the low voltage electrodes 4 are directly cooled with a coolant such as cooling water and the like, while a rise in gas temperature in the discharge gaps 6 may be suppressed by shortening the gap length of the discharge gap 6, and the ozone generating efficiency is increased by increasing the electron temperature, ozone decomposition is inhibited and, as a result, an efficient ozonizer capable of deriving highly concentrated ozone gas may be provided.
In this example, coolant flows from the coolant inlet portion to the coolant passages 11 in each of the low voltage electrodes 4 and is exhausted outside the ozonizer from the coolant outlet portion 12 and the low voltage electrodes 4 are thereby cooled.
In a conventional ozonizer of such a construction, the coolant outlet portion 12 and coolant inlet portion, and the ozone gas outlet portion 10 are formed separately at both sides of the ozonizer, and further, are formed passing through the separate blocks 3 at both sides of the ozonizer. Therefore, there are problems in that time is required to position respective through holes for forming the coolant outlet portion 12, the coolant inlet portion and the ozone gas outlet portion 10, and an assembly operation is time consuming.
Furthermore, the coolant outlet portion 12 and coolant inlet portion, and ozone gas outlet portion 10 are formed separately at both sides of the ozonizer, and there is a problem in that a size of the entire construction is enlarged.
Also, since integration of the base 1, the discharge cells 2 and the blocks 3 is performed by means of the plurality of fastening bolts 5 in both end portions of the ozonizer, the discharge cells 2 may be bent slightly into arc shapes the effect of which is large especially when the discharge gap length is short, 0.1 mm, and there is a problem in that the discharge gap length becomes non-uniform and highly concentrated ozone gas cannot be obtained.
Furthermore, the spacers 9 forming the discharge gap are rigid bodies and the diameter thereof is designed to be smaller than the discharge gap length which is inevitably determined when integrating the base 1, discharge cells 2 and blocks 3 using the fastening bolts 5; such a design entails the following problems.
That is, in a case where the discharge gap length is short and a highly concentrated ozone gas is generated, since a pressure loss of gas flowing across (along the direction of the page surface in FIG. 25) adjacent spacers 9 is much smaller than that of gas flowing along (the direction orthogonal to the page surface in FIG. 25) the spacers 9, much of the oxygen gas flows across adjacent spacers 9, and oxygen gas flowing in from the oxygen gas inlet portion flows toward the ozone gas outlet portion 10 in the end portion and a so-called “short-pass” phenomena occurs in the gas flow, and there is a problem in that an ozone gas generating efficiency is degraded.
In order for the oxygen gas to flow along the spacers 9 and eliminate the occurrence of a short-pass, it is understood that the pressure loss of gas flowing across adjacent spacers 9 must be approximately ten (10) or more the pressure loss of gas flowing along the spacers 9. For example, in the case of an ozonizer where the discharge gap length is 0.1 mm, the space between the spacer 9 and the discharge gap 6 must be very minuscule, the manufacture of the spacers 9 of such dimensions is nearly impossible and a short-pass cannot be avoided.